1. Field of the Invention
This invention relates to a magnetic head device for recording and/or reproducing information signals for a disc-shaped recording medium, such as a magnetic disc, and a disc drive device having this magnetic head device.
2. Description of the Related Art
Heretofore, there is known a disc cartridge comprised of a magnetic disc rotationally housed in a main controller body unit. This removable type of the disc cartridge may be exemplified by a disc cartridge having, as a information recording medium, a magnetic disc with a diameter of 3.5 inch, having a signal recording layer on a flexible disc substrate, or a so-called flexible disc.
The disc drive device, on which the above disc cartridge is loaded and which is adapted to record/reproduce information signals for a magnetic disc, includes a head unit for supporting a head portion having a magnetic head element adapted for recording/reproducing information signals for the magnetic disc, a supporting arm for supporting the head portion at its foremost part, a base plate supporting the proximal end of this supporting arm, and an arm holding member adapted to hold the supporting arm via this base plate. The supporting arm carries a head portion and a base plate at its foremost and rear parts, respectively. The head plate is mounted on an arm holding member. The base plate is mounted on the arm holding member supported on a movement unit.
The disc driving device also includes a disc rotating driving unit, made up of a movement unit for causing movement of the head portion in a direction along the radius of the magnetic disc via head unit, a disc table on which is loaded the magnetic disc and a spindle motor for rotationally driving the disc table.
When the disc cartridge is loaded into the main body portion of the disc driving device, the magnetic disc in the disc cartridge is set on the disc table and run in rotation. The supporting arm of the head unit is moved in the direction along the radius of the magnetic disc via a movement unit to record/reproduce information signals for the magnetic disc by the head portion.
Meanwhile, with an increasing capacity of handled information signals, there is proposed a large capacity disc cartridge holding therein a magnetic disc having an extremely high recording density in order to have the high recording density of tens to hundreds of megabytes in comparison with 2 megabytes of the conventional disc cartridge.
In this type of the large capacity disc cartridge, the track width and the pitch are reduced to assure high density of the recording tracks formed on the signal recording surface. To this end, if the magnetic head is rotationally deflected even to the slightest extent, without following up with the movement of the magnetic disc, due to disturbances, the magnetic head is deviated from the track to be accessed and becomes unable to follow the target recording track for tracking, and hence becomes unable to record/reproduce the information signals accurately.
The disc drive device for recording/reproducing the high capacity disc is configured so that, when recording/reproducing the information signals on the high capacity disc, the high capacity disc is run in rotation at an elevated speed, at the same time as the magnetic head element is slightly floated from the signal recording surface of the high capacity disc.
Moreover, the disc drive device is required to be compatible in the sense that it can record/reproduce information signals of a magnetic disc of the conventional recording density. The disc drive device for recording/reproducing a conventional magnetic disc of the recording capacity of, for example, 2 MB, and a high capacity disc, includes a head unit having two magnetic heads associated with the respective magnetic discs of different recording densities.
Thus, the head unit of the disc drive device, having two magnetic head elements, has the mass approximately ten times that of the magnetic head element owned by, for example, the hard disc drive, such that it is necessary to increase the toughness of the supporting arm.
Since the head portion records/reproduces information signals in the floating state with respect to the signal recording surface of the high capacity disc, the supporting arm needs to support the head portion so that the gap between the head portion and the signal recording surface of the high capacity disc will be of a desired value. That is, the position of the head portion with respect to the signal recording surface needs to be controlled to high accuracy.
Also, since the disc drive device needs to perform fine movement with respect to the recording track of the high capacity disc, designed to have a high recording density, the disc drive device includes a movement unit for causing movement of the supporting arm by electromagnetic driving power. The supporting arm however suffers from the problem that it cannot perform optimum movement if it is in resonant vibrations with the vibrations of the motor of the movement system. In particular, for recording/reproducing the high capacity disc, the supporting arm needs to be configured for evading the resonant frequency with the frequency of the vibrations generated by the spindle motor configured for rotationally driving the high capacity disc.
It is therefore an object of the present invention to provide a magnetic head device that allows for high precision follow-up of the magnetic head element with respect to the signal recording surface of the disc-shaped recording medium, and a disc drive device having this magnetic head device.
According to the present invention, there is provided a magnetic head device in which magnetic head elements can follow the signal recording surface of the first or second magnetic disc. The magnetic head device includes a head portion for recording/reproducing information signals for the first or second magnetic disc, and a supporting arm having a first portion for supporting said head portion, a second portion mounted on a supporting arm holding portion and a third portion interconnecting said first and second portions. The first to third portions of the supporting arm are of different shapes so as to have different physical properties to follow the first or second magnetic disc under a desired condition.
With the above-described magnetic head device, in which the supporting arm includes first to third portions of different shapes, the head portion follows the disc-shaped recording medium under a desired condition, so that the toughness and the resonant frequencies etc of respective portions are set to optimum values.
That is, the first, second or third portion of the supporting arm is shaped in such a manner as to take into account the toughness around an axis parallel to the longitudinal direction of the supporting arm, referred to below as the pitching direction, in order to optimize the initial attitude of the supporting arm relative to the disc-shaped recording medium.
Also, the first, second or third portion of the supporting arm is shaped in such a manner as to take into account the toughness which will realize an optimum value of the gap between the head portion and the signal recording surface of the disc-shaped recording medium, in order to optimize the follow-up characteristics of the head portion to the disc-shaped recording medium.
In addition, the first, second or third portion of the supporting arm is shaped in such a manner as to take into account the toughness around an axis parallel to the width-wise direction of the supporting arm, referred to below as the rolling direction, in order to evade resonance with the vibrations applied from outside.
According to the present invention, there is also provided a disc drive device including a head portion having a magnetic head element for recording and/or reproducing information signals for a disc-shaped recording medium, a supporting arm having a first portion for supporting said head portion, a second portion mounted on a supporting arm holding portion and a third portion interconnecting said first and second portions, and a supporting arm holding member having a receiving portion for receiving the second portion of the supporting arm for mounting therein. The supporting arm holding member holds the supporting arm, movement means for causing movement of the supporting arm holding member in the direction along the radius of the disc-shaped recording medium. The disc drive device of the present invention also includes driving means for rotationally driving the disc-shaped recording medium. The first to third portions of the supporting arm are of different shapes so as to have different physical properties to follow the first or second magnetic disc under a desired condition.
With the above-described disc drive device, in which the supporting arm includes first to third portions of different shapes, the head portion follows the disc-shaped recording medium under a desired condition, so that the toughness and the resonant frequencies etc of respective portions are set to optimum values.
That is, since the first portion, second portion or the third portion of the supporting arm is shaped to take into account the toughness in the pitching direction of the supporting arm, it is possible to optimize the initial attitude of the supporting arm with respect to the disc-shaped recording medium.
Also, since the first, second or third portion of the supporting arm is shaped in such a manner as to take into account the toughness which will realize an optimum value of the gap between the head portion and the signal recording surface of the disc-shaped recording medium, it is possible to optimize the follow-up characteristics of the head portion to the disc-shaped recording medium.
In addition, since the first portion, second portion or the third portion of the supporting arm is shaped to take into account the toughness in the rolling direction of the supporting arm, it is possible to evade resonance with vibrations produced by the movement means and the driving means.
With the disc drive device according to the present invention, it is possible to achieve high-precision follow-up of the head portion to the disc-shaped recording medium via the supporting arm. Thus, with the present disc drive device, it is possible to improve reliability in the recording/reproducing operation.
With the disc drive device according to the present invention, it is possible to achieve high-precision follow-up of the head unit to the disc-shaped recording medium via the supporting arm. Thus, with the present disc drive device, it is possible to improve reliability in the recording/reproducing operation.